The present invention concerns an improved process for the selective electrochemical reduction of halogenated 4-aminopicolinic acids.
U.S. Pat. No. 6,352,635 B2 describes the preparation of certain herbicidal 3-halo-4-aminopicolinic acid derivatives by the electrochemical reduction of certain 3,5-dihalo-4-aminopicolinic acid derivatives. In this process, the silver cathode is either activated by anodization in the presence of 2 percent sodium hydroxide and 1 percent sodium chloride, or anodized in the presence of starting material to be reduced and 1 to 3 weight percent of excess NaOH. Because of passivation, however, it is usually necessary to reactivate the cathode by anodization in the presence of the electrolyte to finish a batch. It would be desirable to have an improved method for activating the cathode that is more resistant to passivation.